En proceso de actualización........

167.-David Elorriaga, Fernando Carrillo-Hermosilla*, Antonio Antiñolo*, Isabel López-Solera, Bérengère Menot, Rafael Fernández-Galán, Elena Villaseñor, Antonio Otero.

“New Alkyl Imido Niobium Complexes Supported by Guanidinate Ligands: Synthesis, Characterization and Migratory Insertion Reactions”

Organometallics, 2012 Aceptado In press

166.- Antonio Antiñolo, Khédidja Dorani, Santiago García-Yuste, Isabel López-Solera, Antonio Otero,María Teresa Tercero-Morales, Gábor Kovács, Gregori Ujaque, Agustí Lledós

“Experimental and Theoretical Studies of the Hydrogenation of α,β-Unsaturated Acids by an 18e Hydridecarbonyl niobocene Complex”

Organometallics, 2012 submitted

165.- Carlos Alonso-Moreno, Antonio Antiñolo,  Santiago García-Yuste, Isabel López-Solera, Antonio Otero,María Teresa Tercero-Morales Molecular Structure of a Hydrideniobocene Complex [Nb(h⁵-C₅H₄SiMe₃)₂(H)₃], and their Use as Catalyst for Ring-Opening Polymerization of Cyclic Esters

Eur. J. Inorg. Chem.  2012, Aceptado In press

164.- Antonio Antiñolo, Fernando Carrillo-Hermosilla, Victorio Cadierno, Joaquín García-Álvarez, and Antonio Otero

"MW-assisted Meyer-Schuster rearrangement of propargylic alcohols catalyzed by the oxovanadate complex [V(O)Cl(OEt)2]"

ChemCatChem 2012, 4, 123 – 128

163.- R. Reguillo-Carmona, A. Antiñolo, S. García-Yuste, I. López-Solera  y A. Otero

Lewis base character of the phosphorus atom in phosphanido-niobocene complexes. Synthesis of new early–early homo- and heterobimetallic entities

Dalton Trans., 2011, 40, 2622–2630

162.- Antonio Antiñolo, Rafael Fernández-Galán, Noelia Molina, Antonio Otero, Iván Rivilla, Ana M. Rodríguez

“C-ansa-zirconocene complexes with O/S donor ligands: Novel homoleptic six coordinate 4-mercaptophenolate complex of Zr(IV)”

Inorganica Chimica Acta 363 (2010) 3489-3497

161.- Antonio Antiñolo, Santiago García-Yuste, Antonio Otero, Rebeca Reguillo-Carmona, María Teresa Tercero-Morales

“An easy and direct synthetic route to phosphamido niobocenes through nucleophilic attack of phosphide niobocene complexes on acyl halides

C. R. Chimie 13 (2010) 929–934

160.-Javier Romero-Fernandez, Fernando Carrillo-Hermosilla, Antonio Antiñolo, Carlos Alonso-Moreno,

Ana M. Rodríguez, Isabel López-Solera and Antonio Otero

Oxo- and imido-alkoxide vanadium complexes as precatalysts for the guanylation of aromatic amines

Dalton Trans., 2010, 39, 6419–6425

159.-Carlos Alonso-Moreno, Fernando Carrillo-Hermosilla, Andrés Garcés, Antonio Otero, Isabel Lopez-Solera, Ana M. Rodríguez and Antonio Antiñolo.

Simple, Versatile, and Efficient Catalysts for Guanylation of Amines

Organometallics 2010, 29, 2789–2795

158.-Antonio Antiñolo, Santiago García-Yuste, Isabel Lopez Solera, Antonio Otero, Juan Carlos Pérez-Flores, Rebeca Reguillo-Carmona, Elena Villaseñor, Eva Santos, Erik Zuidema and Carles Bo.

Reactions of alkynes with phosphido niobocenes: a combined experimental and theoretical study

Dalton Trans., 2010, 39, 1962–1971

157.-Carlos Alonso-Moreno, Pedro Carrión, Fernando Carrillo-Hermosilla, Antonio Antiñolo and Antonio Otero

UV–visible spectroscopy for zirconocene activation by MAO in olefin polymerization: activity versus wavenumber

Appl. Organometal. Chem. 2009 , 23, 241–244

156.-Antonio Antiñolo , Rafael Fernández-Galán , Noelia Molina , Antonio Otero , Iván Rivilla ,Ana M. Rodríguez

New alkenyl-substituted group 4 C-ansa-metallocene complexes. Reactivity of the substituent at the carbon ansa bridge

Journal of Organometallic Chemistry 694 (2009) 1959–1970

155.- Javier Romero, Fernando Carrillo-Hermosilla, Antonio Antiñolo, Antonio Otero

Homogeneous and supported bis(imino)pyridyl vanadium(III) catalysts

Journal of Molecular Catalysis A: Chemical 304 (2009) 180–186

 154.-Carlos Alonso-Moreno, Fernando Carrillo-Hermosilla, Javier Romero-Fernández, Ana M. Rodríguez, Antonio Otero, Antonio Antiñolo

Well-Defined Regioselective Iminopyridine Rhodium Catalysts for Anti-Markovnikov Addition of Aromatic Primary Amines to 1-Octyne

Adv. Synth. Catal. 2009, 351, 881 – 890

153.- Antonio Otero , Juan Fernández-Baeza a, Antonio Antiñolo , Juan Tejeda , Agustín Lara-Sánchez a, Luis F. Sánchez-Barba, Margarita Sánchez-Molina , Carles Bo, Manuel Urbano-Cuadrado
Hybrid scorpionate/cyclopentadienyl titanium and zirconium complexes with alkoxide and imido ligands

Inorganica Chimica Acta 362 (2009) 2909–2914

152.-Carlos Alonso-Moreno, José Sancho, Fernando Carrillo-Hermosilla, Antonio Otero, Antonio Antiñolo, Isabel López-Solera

 Synthesis, Characterization and Compared Reactivity of Asymmetrical ansa-Metallocenes
Inorganic Chemistry Communications, 2009,12, 184-186

151.- Antonio Antiñolo, Santiago García-Yuste, Antonio Otero, Rebeca Reguillo-Carmona

“Insertion Reactions of Isothiocyanates into the Nb–P Bond of Phosphide-Niobocene Complexes”.

Eur. J. Inorg. Chem.  2009, 539-544

150.- S. Gómez-Ruiz, A. Garcés, S. Prashar, M. Fajardo, A. Antiñolo, A. Otero,

Synthesis,characterization and applications in ethylene polymerization of asymmetric ansa-titanocene complexes. Molecular structure of [Ti{Me₂Si(η 5-C₅Me₄)(η 5-C₅H₃ iPr}Cl₂],

Inorg. Chim. Acta 2009, 362, 1042-1046  

149. - Ortiz, M., Torréns, M., Mola, J.L., Ortiz, P.J., Fragoso, A., Díaz, A., Cao, R., Prados, P., De Mendoza, J., Otero, A., Antiñolo, A., Lara, A.

Nitric oxide binding and photodelivery based on ruthenium (II) complexes of 4-arylazo-3,5-dimethylpyrazole

Dalton Transactions, 2008. 3559-3566

148.- Antonio Otero, Juan Fernández-Baeza, Agustín Lara-Sánchez, Antonio Antiñolo, Juan Tejeda, Emilia Martínez-Caballero, Isabel Márquez-Segovia, Isabel López-Solera, Luis F. Sánchez-Barba, and Carlos Alonso-Moreno.

Versatile Scorpionates and New Developments in the Denticity Changes of NNCp Hybrid Scorpionate/Cyclopentadienyl Ligands in Sc and Y Compounds: From κ1-Nη5-Cp to κ2-NNη5-Cp

Inorg. Chem. 47(2008)4996

147.- Carlos Alonso-Moreno, Andrés Garcés, Luis F. Sánchez-Barba, Mariano Fajardo, Juan Fernández-Baeza, Antonio Otero, Agustín Lara-Sánchez, A. Antiñolo, L. Broomfield, M. I. López-Solera, and A. M. Rodríguez

Discrete Heteroscorpionate Lithium and Zinc Alkyl Complexes. Synthesis, Structural Studies, and ROP of Cyclic Esters
 Organometallics 2008, 27, 1310–1321

146.- Pedro J. Aragón Sáez, Fernando Carrillo-Hermosilla, Elena Villaseñor, Antonio Otero, Antonio Antiñolo, and Ana M. Rodríguez

Heterocycle-Substituted Indenes as Precursors for Supported Zirconocene Catalysts

Eur. J. Inorg. Chem.  2008, 330-337

145.-Antonio Otero, Juan Fernández-Baeza, Antonio Antiñolo, Agustín Lara-Sánchez, Emilia Martínez-Caballero, Juan Tejeda,Luis F. Sánchez-Barba, Carlos Alonso-Moreno, and Isabel López-Solera

Scandium and Yttrium Complexes Supported by CNP Heteroscorpionate Ligands: Synthesis, Structure, and Polymerization of e-Caprolactone

Organometallics 2008, 27, 976–983

144.-Luis F. Sanchez-Barba, Andres Garcés, Mariano Fajardo, Carlos Alonso-Moreno, Juan Fernández-Baeza, Antonio Otero,  Antonio Antiñolo, Juan Tejeda, Agustín Lara-Sánchez, and María I. López-Solera

Well-Defined Alkyl Heteroscorpionate Magnesium Complexes as Excellent Initiators for the ROP of Cyclic Esters

Organometallics 2007, 26, 6403-6411

143.- Otero, A., J. Fernandez-Baeza, A. Antinolo, J. Tejeda, A. Lara-Sanchez, L. F. Sanchez-Barba, M. Sanchez-Molina, S. Franco, M. I. Lopez-Solera, A. M. Rodriguez.

Highly diastereoselective nucleophilic addition to myrtenal. Straightforward synthesis of an enantiopure scorpionate ligand.

Inorg. Chem. 46(2007)8475-8477

142.-Santiago Gómez-Ruiz, Dorian Polo-Cerón, Sanjiv Prashar, Mariano Fajardo, Antonio Antiñolo, Antonio Otero

Synthesis and reactivity of alkenyl substituted zirconocene complexes and their application as olefin polymerization catalysts

Eur. J. Inorg. Chem.  2007, 4445–4455

141.- Otero, A; Fernandez-Baeza, J; Antiñolo, A; Tejeda, J; Lara-Sanchez, A; Sanchez-Barba, LF; Sanchez-Molina, M; Rodriguez, AM; Bo, C; Urbano-Cuadrado, M

Expanding heteroscorpionates. Facile synthesis of new hybrid scorpionate/cyclopentadienyl ligands and their lithium and group 4 metal compounds: A combined experimental and density functional theory study 
Organometallics 2007, 26, 4310-4320

140.- Antonio Antiñolo, Santiago García-Yuste, Antonio Otero, Elena Villaseñor

On the Insertion Processes of Unsaturated Molecules Into Nb-X sigma Bond of Cp'₂NbX Moieties ( Cp'=h⁵-C₅H₄SiMe₃, X= H, C, P)

J.Organomet. Chem.  692 (2007) 4436–4447

139.-Santiago Gómez-Ruiz a, Sanjiv Prashar, Mariano Fajardo, Antonio Antiñolo, Antonio Otero.

Synthesis, structural characterization and reactivity of new tin bridged ansa-bis(cyclopentadiene) compounds: X-ray crystal structures of Me₂Sn(C₅Me₄R-1)₂ (R = H, SiMe₃)

J.Organomet. Chem.  692 (2007) 3057-3064

138.-Dorian Polo-Cerón, Santiago Gómez-Ruiz, Sanjiv Prashar, Mariano Fajardo, Antonio Antiñolo and Antonio Otero

“Synthesis Of Bulky Zirconocene Dichloride Compounds And Applications In Olefin Polymerization”

Collect. Czech. Commun. 2007, Vol. 72, Nos. 5–6, pp. 747–763

137.- Antonio Antiñolo, Santiago García-Yuste, Antonio Otero, Juan C. Pérez-Flores, Maria Isabel Lopez-Solera , Ana M. Rodríguez,

“Reactivity of hydride-niobocenes towards heterocycles with hydroxide, -mercapto or -amine functionalities. X-ray molecular structure of [(h⁵-C₅H₄SiMe₃)₂Nb(CNXylyl)₂][I₃] and  [(h⁵-C₅H₄SiMe₃)₂Nb(H)(P(OMe)₃)]·(bzta)’-NH₂. ((bzta)’-NH₂=2-amino-6-methylbenzothiazol)”.

J.Organomet. Chem.  692 (2007) 3328–3339

136.- Antonio Otero, Juan Fernandez-Baeza, Antonio Antiñolo, Juan Tejeda, Agustin Lara-Sánchez, Luis F. Sánchez-Barba, Isabel Lopez-Solera, and Ana M. Rodriguez

“Lithium, Titanium, and Zirconium Complexes with Novel Amidinate Scorpionate Ligands”

Inorg. Chem. 46(2007)1760-1770

135.- Dorian Polo-Cerón a, Santiago Gómez-Ruiz a, Sanjiv Prashar, Mariano Fajardo, Antonio Antiñolo, Antonio Otero, Isabel López-Solera, Manuel L. Reyes.

“Synthesis of chiral unbridged zirconocene complexes: Applications in the polymerization of ethylene and propylene”

Journal of Molecular Catalysis A: Chemical 268 (2007) 264–276

134.-Santiago Gómez-Ruiz a, Sanjiv Prashar, Luis F. Sánchez-Barba, Dorian Polo-Cerón, Mariano Fajardo , Antonio Antiñolo, Antonio Otero, Miguel A. Maestro, César J. Pastor

“Synthesis and catalytic applications of C1 symmetric group 4 ansa-metallocene complexes”

Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269

133.- Antonio Otero, Juan Fernández-Baeza, Antonio Antiñolo, Juan Tejeda, Agustin Lara-Sánchez, Luis Sánchez-Barba, Margarita Sánchez-Molina, Sonia Franco, Isabel López-Solera and Ana M. Rodríguez

“Design of new heteroscorpionate ligands and their coordinative ability toward Group 4 transition metals; an efficient synthetic route to obtain enantiopure ligands”

Dalton Trans.  2006, 4359-4370

132.- Pedro Carrión, Fernando Carrillo-Hermosilla, Carlos Alonso-Moreno, Antonio Otero, Antonio Antiñolo, José Sancho, Elena Villaseñor

“Supported modified zirconocene catalyst for ethylene polymerization.”

Journal of Molecular Catalysis A: Chemical 258(2006)236-245

131.- Andrés Garcés, Yolanda Pérez , Santiago Gómez-Ruiz, Mariano Fajardo , Antonio Antiñolo , Antonio Otero , Carmen López-Mardomingo , Pilar Gómez-Sal , Sanjiv Prashar,

“Synthesis of Niobocene Imido Cations. X-ray crystal structure of [Nb(=NBu^t)(η⁵-C₅H₄SiMe₃)₂(CNBu^t)][BPh₄]”

J.Organomet. Chem.  691, 2006, 3652-3658

130. Antonio Antiñolo, David Evrard, Santiago García-Yuste, Antonio Otero, Juan C. Pérez-Flores, Rebeca Reguillo-Carmona, Ana M. Rodríguez, Elena Villaseñor

Synthesis, Reactivity  and  X-Ray Diffraction Structures of New Isocyanideniobocene Complexes: [Nb(h⁵-C₅H₄SiMe₃)₂(CNR)(PMePh₂)]X, R=Xylyl, Cy and [Nb(h⁵-C₅H₄SiMe₃)₂(P(I)Ph₂)(CNXylyl)]I₃

Organometallics 2006, 25, 3698-3705

 I. DORADO, A. GARCÉS, C. LÓPEZ-MARDOMINGO, M. FAJARDO, A. RODRÍGUEZ, A. ANTIÑOLO, A. OTERO
Synthesis and structural characterización of new organo-diimido and organo-imido niobium and titanium complexes
J. Chem. Soc., Dalton Trans., 2375-2382, (2000).
 

C. GARCÍA-YEBRA, C. LÓPEZ-MARDOMINGO, M. FAJARDO, A. ANTIÑOLO, A. OTERO, A. RODRÍGUEZ, A. VALLAT, D. LUCAS, Y MUGNIER, J.J. CARBÓ, A. LLEDÓS, C. BO
Facile synthesis of alkynyl- and vinylidene-niobocene complexes. Unexpected h1-vinylidene-h2-alkyne isomerization
Organometallics, 19: 1749-1765, (2000).
 

A. ANTIÑOLO, I. DEL HIERRO, I. LÓPEZ-SOLERA, S. GARCÍA-YUSTE, A. OTERO, M. FAJARDO, A. RODRÍGUEZ
Synthesis and reactivity of new oxo alkyl or oxo acyl niobocene complexes and crystal structure of Cp'2Nb(=O(OC(O)CF3)(Cp'=h5-C5H4SiMe3)
Journal of Organometallic Chemistry, 598: 167-173, (2000).
  

C. GARCÍA-YEBRA, F. CARRERO, C. LÓPEZ-MARDOMINGO, M. FAJARDO, A. RODRÍGUEZ, A. ANTIÑOLO, A. OTERO, D. LUCAS, I. MUGNIER
New niobocene alkyne complexes: synthesis and characterization of neutral and cationic niobium complexes with functionalized alkynes. X-ray crystal structure of [Nb(? 5- C5H4SiMe3)2(Cl)(? 2(C,C)-R1C? CR2)](R1 = C? CPh, R2 = Ph (2b); R1 = CH2CH=C(CH3)2, R2 = Ph (3b)
Organometallics, 18: 1287-1298, (1999)
  

A. ANTIÑOLO, M. FAJARDO, C. HUERTA, A. OTERO, S. PRASHAR, A. M. RODRÍGUEZ
Sandwich and half-sandwich niobium imido complexes: X-ray crystal structure of [Nb(=NAr)Cp'2Cl] (Cp' = h5-C5H4SiMe3, Ar = C6H4OMe-4)
Journal of Organometallic Chemistry, 585: 154-161, (1999)
  

C. GARCÍA-YEBRA, A. ANTIÑOLO, F. CARRILLO-HERMOSILLA, M. FAJARDO, J. FERNÁNDEZ-BAEZA, S. GARCÍA-YUSTA, A. OTERO
Advances in the chemistry of bis-cyclopentadienyl hydride derivatives of niobium and tantalum.
Coord. Chem. Rev., 193 (195):43-72, (1999)
      

Z. M. TEHRANI, D. LUCAS, Y. MUGNIER, A. ANTIÑOLO, A. OTERO, M. FAJARDO, A. GARCÉS, C. LÓPEZ-MARDOMINGO
Electrocatalytic process in the reduction of {Nb[h5-C5H4(SiMe3)]2(Cl)(NHPh)}BF4
Journal of Organometallic Chemistry, 548:309-313, (1997)
   

A. ANTIÑOLO, F. CARRILLO-HERMOSILLA, A. OTERO, M. FAJARDO, A. GARCÉS, P. GÓMEZ-SAL, C. LÓPEZ-MARDOMINGO, A. MARTÍN, C. MIRANDA
Synthesis and structural characterization of isocyanate, amido and imido niobocene derivatives:crystal structures of [Nb(h5-C5H4SiMe3)2Cl(k2N,C-OCNPh] and [{Nb(h5-C5H4SiMe3)2Cl}2-(m-1,3-N2C6H4)
J. Chem. Soc., Dalton Trans., 59-65, (1998)
   

A. ANTIÑOLO, F. CARRILLO-HERMOSILLA, A. CASTEL, M. FAJARDO, J. FERNÁNDEZ-BAEZA, M. LANFRANCHI, A. OTERO, M. A. PELLINGHELLI, G. RIMA, J. SATGÉ, E. VILLASEÑOR
Synthesis and characterization of the first niobocene germyl complexes and reactivity of triphenylsilyl-, triphenylgermyl-, and triphenylstannylniobocene derivatives. X-ray molecular structures of d0 Nb(h5-C5H4SiMe3)2(H)2(EPh3) (E = Ge, Sn)
Organometallics, 17:1523-1529, (1998)
     

A. Antiñolo; F. Carrillo-Hermosilla; S. García-Yuste; M. Freitas; A. Otero; S. Prashar; E. Villaseñor; M. Fajardo
Inorg. Chim. Acta 1997, 259, 101-105.
Insertion reactions of heterocumulenes into the niobium-hydride bond of isocyanide and carbonyl niobocene complexes
The reaction of the hydride niobocene complexes, Nb(eta(5)- C5H4SiMe3)(2)(H) (CNR) (R = 2,6-dimethylphenyl (Xylyl) orcyclohexyl (Cy)) and Nb(eta(5)-C5H4SiMe3)(2)(H)(CO) with the heterocumulenes PhN = C = X (X = O or S) affords the new formamido and thioformamido complexes Nb(eta(5)-C5H4SiMe3)(2)(CNR) (eta(1)-XC(H)NPh) (R = Xylyl, X = O (1); R=Xylyl, X = S (2); R = Cy, X = O (3); R = Cy, X = S (4)) and Nb(eta(5)-C5H4SiMe3)(2)(CO) (eta(1)-XC(H)NPh) (X = O (5); X = S (6)). The protonation of these derivatives using HCF3COO yields the trifluoroacetato complexes Nb(eta(5)-C5H4SiMe3)(2)(CNR) (eta(1)- OOCCF3) (R = Xylyl (7); R = Cy (8)) and Nb(eta(5)-C5H4SiMe3)(2)(CO) (eta(1). OOCCF3) (9) and the imine derivatives HOC(H) = NPh and HSC(H) = NPh. Thermal treatment of 5 gives the eta(2)-formamido complex Nb(eta(5)-C5H4SiMe3)(2)(eta(2)-OC(H)NPh) (10). All these complexes have been characterised by spectroscopic methods.
 

A. Antiñolo; F. Carrillo-Hermosilla; M. Fajardo; S. García-Yuste; A. Otero; S. Camanyes; F. Maseras; M. Moreno; A. Lledós; J. M. Lluch
J. Am. Chem. Soc. 1997, 119, 6107-6114.
Synthesis and Spectroscopic Properties of Dihydrogen Isocyanide Niobocene [Nb(h⁵-C₅H₄SiMe₃)₂(h²-H₂)(CNR)]⁺ Complexes. Experimental and Theroretical Study of the Blocked Rotation of a Coordinated Dihydrogen
Synthesis of stable hydride isocyanide derivatives Nb(eta(5)- C5H4SiMe3)(2)(H)(CNR) has been achieved through the formation of coordinatively unsaturated 16-electron species Nb(eta(5)- C5H4SiMe3)(2)H by thermolytic loss of H-2 followed by the coordination of an isocyanide ligand. Low-temperature protonation with a slight excess of CF3COOH leads to the eta(2)-dihydrogen complexes [Nb(eta(5)-C5H4SiMe3)(2)(eta(2)-H-2)(CNR)](+). NMR spectra of these H-H complexes and their monodeuterated H-D isotopomers present a single high-field resonance at room temperature. By lowering the temperature to 178 K, decoalescence of the signal was observed for the H-D complexes but not for the H-H ones. By combining DFT electronic structure calculations with a monodimensional rotational tunneling model, it has been shown that the absence of decoalescence of the H-H signal is due to the existence of a very large exchange coupling. Conversely, for the H-D isotopomer, the difference in zero point energy corresponding to two nonequivalent (H- D and D-H) positions leads to a slight asymmetry which dramatically reduces the exchange coupling, allowing decoalescence to be observed. Therefore, the H-D classical rotation and the quantum exchange processes will not be practically observed for this complex, whereas only the classical process for the H-H species is quenched out on the NMR time scale.
   

A. Antiñolo; A. Otero; M. Fajardo; R. Gil-Sanz; M. J. Herranz; C. López-Mardomingo; A. Martín; P. Gómez-Sal
J. Organomet. Chem. 1997, 533, 87-96.
Synthesis, structure, and chemistry of hydrido and alkyl niobocene Ketene and Ketenimine derivatives. X-ray crystal structure of [Nb(h⁵-C₅H₄SiMe₃)₂(CH₃)(h²-(C,O)O=C=CPh₂)]
[Nb(eta(5)-C5H4SiMe3)(2)Cl(eta(2)-(C,Z)-ZCCRPh)] (1a, Z = NPh, R = Ph; 1b, Z = NPh, R = Me; 1c, Z = NPh, R = Et; 1d, Z = NPh, R = H; 2, Z = O, R = Ph) reacts with Li(BEt3H) and with Grignard (RMgI) or dialkyl magnesium (R2Mg) reagents to give the hydride niobocene complexes [Nb(eta(5)-C5H4SiMe3)(2) H(eta(2)-(C,Z)-ZCCRPh)] (3a, Z = NPh, R = Ph; 3b, Z = NPh, R = Me; 3c, Z = NPh, R = Et; 3d, Z = NPh, R = H, 4, Z = O, R = Ph) and the alkyl niobocene complexes [Nb(eta(5)- C5H4SiMe3)(2)R(eta(2)-(C,Z)-ZCCR'Ph) (5a, Z = NPh, R = Me, R' = Ph; 5b, Z = NPh, R = R' = Me; 5c, Z = NPh, R = Me, R' = Et; 5d, Z = NPh, R = Me, R' = H; 6a, Z = O, R = Me, R' = Ph; 6b, Z = O, R = Et, R' = Ph) respectively. The molecular structure of 6a was determined by single-crystal diffractometry. It shows a typical bent-metallocene geometry around the niobium atom with the eta(2)(C,O) ketene and methyl groups arrayed in the plane between the two cyclopentadienyl rings. Finally, some hydride and alkyl niobocene ketenimine and ketene complexes were easily protonated with 1 equiv. Of HBF4 . OEt2 giving rise, in one step, to the corresponding eta(2)-iminoacyl and eta(2)-acyl complexes [Nb(eta(5)-C5H4SiMe3)(2)Y(eta(2)-(C,Z)- ZCCRHPh)](+) +[BF4-] (7a, Y = H, Z = NPh, R = Ph; 7b, Y = H, Z = NPh, R = Me; 8a, Y = Me, Z = NPh, R = Ph; 8b, Y = Me, Z = NPh, R = Et; 9, Y = Me, Z = O, R = Ph). H-1 NMR studies on several unsymmetrical ketenimine-bearing chloro, hydride and methyl niobocene complexes containing E-Z isomeric mixtures were carried out, and it was found that intermolecular isomerization of the E and Z isomers may govern the different observed E-Z ratios. The structures of the different families of complexes were determined by spectroscopic methods.
   

A. Antiñolo; F. Carrillo-Hermosilla; I. D. Hierro; A. Otero; M. Fajardo; Y. Mugnier
Organometallics 1997, 16, 4161-4166.
Synthesis and Characterization of New Alkyl-Carbon Dioxide Compounds and the First Neutral Acyl-Carbonyl Niobocene Complexes
The olefin-hydride complexes Cp-2'Nb(H)(eta(2)-RHC=CH2) (Cp' = eta(5)- C5H4SiMe3; R = H (3), C6H5 (4, endo isomer)) were prepared by the alkylation reactions of [Cp-2'NbCl](2) (1) with the appropriate Grignard reagents RMgX (R = CH2CH3, CH2CH2C6H5) followed by a stereoselective beta-elimination from the intermediate alkyl complexes Cp-2'Nb(CH2CH2R). Complexes Cp-2'Nb(H)(eta(2)-RHC=CH2) (R = C6H4CH3 (5), C6H4OCH3 (6)) were prepared as a mixture of endo and exo isomers by reaction of Cp-2'NbH3 (2) with the corresponding olefin. Furthermore, reactions of CO with 3 and 4, and the reactions of CO2 with 3-6, afforded the alkylniobocene complexes Cp-2'Nb(CO)R (R = CH2CH3 (7), CH2CH2C6H5 (8)) Cp-2'Nb(eta(2)-CO2)(R) (R = CH2CH3 (9)), CH2CH2C6H5 (10), CH2CH2C6H4CH3 (11), CH2CH2C6H4OCH3 (12)). The reactivity of 9 and 10 toward the strong Lewis acid B(C6F5)(3) was also studied; in a first step the adducts Cp-2'Nb(eta(2)-CO2- B(C6F5)(3))(CH2CH2R) (R = H (13), C6H5 (14)) were formed and subsequently evolved to give the oxo-alkyl complexes Cp-2'Nb(O- B(C6F5)(3))(CH2CH2R) (R = H (15), C6H5 (16)) with the loss of CO. Finally, reactions of 3 and 4 with CO under appropriate conditions gave the neutral acylniobocene complexes Cp-2'Nb(CO)(eta(1)- C(O)CH2CH2R) (R = H (17), C6H5 (18)), which were alternatively prepared from the reactions of 7 and 8 with CO. The different complexes were characterized by spectroscopic methods.
 

A. Antiñolo; A. Otero; M. Fajardo; C. García-Yebra; C. López-Mardomingo; A. Martín; P. Gómez-Sal
Organometallics 1997, 16, 2601-2611.
Niobocene Alkyne Complexes: Synthesis and Characterization of Neutral and Cationic d² Metal Alkyne Derivatives. X-ray Crystal Structure of [Nb(h⁵-C₅H₄SiMe₃)₂(h²(C,C)-HC=CPh)(CH₂Ph)]
The paramagnetic niobocene alkyne complexes Nb(eta(5)- C5H4SiMe3)(2)(eta(2)(C,C)-RC=CR') (2) have been synthesized from Nb(eta(5)-C5H4SiMe3)(2)(eta(2)(C,C)-RC=CR')(Cl) (1) and subsequently oxidized in the presence of different ligands to give stable cationic d(2) derivatives, [Nb(eta(5)C(5)H(4)SiMe(3))(2)(eta(2)(C,C)- RC=CR')(L)][BPh4] (L = CH3CN, R = R' = Ph (3a); L = CH3CN, R = R' = CO2Me (3b); L = CH3CN, R = R' = Me (3c); L = CH3CN, R = Me, R' = CO2Me (3d); L = tBuCN, R = R' = Ph (4a); L = tBuCN, R = R' = CO2Me (4b); L = tBuCN, R = R' = Me (4c); L = tBuCN, R = Me, R' = CO2Me (4d); L = tBuNC, R = R' = Ph (5a); L = tBuNC, R = R' = CO2Me (5b); L = tBuNC, R = R' = Me (5c); L = THF, R = R' = Me (6c); L = THF, R = Me, R' = CO2Me (6d); L = Py, R = R' = Ph (7a); L = Py, R = R' = Me (7c)). Oxidation of the complex Nb(eta(5)-C5H4SiMe3)(2)(eta(2)(C,C)- MeC=CCO2Me) (2d) under different experimental conditions gave rise to the divinylidene binuclear d(2) niobocene complex [(eta(5)- C5H4SiMe3)(2)(CO)Nb=C=C(CH3)(CH3)C=C=Nb(CO)(eta(5)- C5H4SiMe3)(2)][BPh4](2) (8a). A mechanism involving the intermediacy of a sigma-acetylide species is proposed for the formation of this compound. Thus, the divinylidene complex [(eta(5)-
 

A. Antiñolo; F. Carrillo-Hermosilla; B. Chaudret; M. Fajardo; J. Fernández-Baeza; M. Lanfranchi; H. H. Limbach; M. Maurer; A. Otero; M. A. Pellinghelli
Inorg. Chem. 1996, 35, 7873-7881.
Exchange Coupling in Niobocene Trihydrides, Nb(C₅H₃RR')₂H₃, and Their Adducts with Copper Triad Cations, [{Nb(C₅H₃RR')₂H₃}₂M]⁺ (R=R'=H; R=H,R'=SiMe₃, R=R'=SiMe₃; M=Cu, Ag, Au)
The reactions of Nb(C(5)H(3)RR')(2)Cl-2 with Red-Al followed by hydrolysis yield Nb(C(5)H(3)RR')(2)H-3 (R = R' = H, 1; R = H, R' = SiMe(3), 2; R = R' = SiMe(3), 3). These compounds react with Lewis acidic coinage cationic species, namely, [Cu(MeCN)(4)]PF6, AgBF4, and ''Au(THT)PF6'', prepared in situ from AuCl(THT) and TIPF6 in a 2 to 1 ratio to yield the adducts [{Nb(C(5)H(3)RR')(2)H-3}(2)M](+) (M = Cu, R = R' = H, 7; R = H, R' = SiMe(3), 8; R = R' = SiMe(3), 9; M = Ag, R = H, R' = SiMe(3), 10; R = R' = SiMe(3), 11; M = Au, R = R' = H, 12; R = H, R' = SiMe(3), 13; R = R' = SiMe(3), 14). Like 1, but unlike the corresponding tantalum derivatives Ta(C(5)H(3)RR')(2)H-3 (R = R' = H, 4; R = H, R' = SiMe(3), 5; R = R' = SiMe(3), 6), 2 and 3 show exchange couplings in their high-field H-1 NMR spectra due to a hydride tunneling phenomenon. The magnitudes of exchange couplings are larger in the cases of 2 and 3 than in the case of 1 as a result of the decrease of electron density upon increasing the number of SiMe(3) substituents on the Cp ring. The addition of a Lewis acidic cation results in the observation of an AB(2) pattern for the hydrides at room temperature, which splits at low temperature into an ABC one in agreement with a fluxional behavior of the cation which binds to two hydrides of each niobium center. The activation energy of these fluxional processes are close to 42-45 kJ . mol(-1) in the case of Cu adducts, 37 kJ . mol(-1) in the case of Ag adducts, and 40 kJ . mol(-1) in the case of Au adducts. The magnitude of exchange couplings is reduced upon addition of copper cation to 1-3, is of the same order of magnitude after addition of a silver cation, and is greatly increased by addition of a gold cation. A model is proposed to explain these variations which involves two isomeric states that are close in energy, one involving two bridging and one terminal hydrides on niobium and one involving one bridging hydride and a dihydrogen molecule. A line shape analysis experiment carried out on 14 allows determination of the parameters of the classical exchange, the coupling constants at various temperatures which reach 550 Hz at 347 K, and the parameters of the quantum mechanical exchange according to our proposed model. The structure of 14 has been studied by X-ray diffraction. The structure has been Solved from diffractometer data by Patterson method and refined by blocked full-matrix least squares on the basis of 3082 observed reflections to R and R(w) values of 0.0346 and 0.0381, respectively. The structure shows the presence of two bridging hydrides between the niobium and gold atoms; one of them is found close to the terminal hydride.
 

S. E. Krami; Y. Mourad; D. Lucas; Y. Mugnier; A. Antiñolo; M. Fajardo; S. García-Yuste; A. Otero
J. Organomet. Chem. 1996, 525, 125-131.
Electrochemical synthesis and reactivity of carbonato-niobocene complexes
The addition of the CO32- dianion to the electrogenerated species Nb(eta(5)-C(5)H(5)RR')(2)Cl (2: R = H, R' = SiMe(3); 2': R = R' = SiMe(3)) gives in ca. 50% yields the anionic carbonate niobium(III) complex [Nb(eta(5)-C(5)H(3)RR')(2)(O (C) over bar(O)O-O,O')](-) (3: R = H, R' = SiMe(3); 3': R = R' = SiMe(3)) which are oxidized electrochemically to the corresponding paramagnetic niobium(IV) complex [Nb(eta(5)- C(5)H(3)RR')(2)(OC(O)O-O,O')] (5: R = H, R' = SiMe(3); 5': R = R' = SiMe(3)). These paramagnetic derivatives have been characterized by ESR and IR spectroscopy. Mechanistic aspects concerning the formation of 3 and 3' are discussed. 3 can also be obtained from two-electron reduction of Nb(eta(5)-C(5)H(4)SiMe(3))(2)(O)Cl, 4, in the presence of carbon dioxide. The addition of the formate anion HCO2- to 3 gives the formato complex Nb(eta(5)-C(5)H(4)SiMe(3))(2)(OC(O)H-O,O') 6.

D. Lucas; Z. Modarres-Tehrani; Y. Mugnier; A. Antiñolo; I. Del Hierro; A. Otero; M. Fajardo
New J. Chem. 1996, 20, 385-391.
New nitrile niobocene complexes; electrochemical studies on their h1/h2 nitrile isomerization processes
The one-electron reduction of Nb(eta(5)- C(5)H(3)RR')(2)X(2) (1:R=SiMe(3), R'=H, X=Cl; 1'; R=SiMe(3), R'=H, X=Br; 1 '': R=R'=SiMe(3), X=Cl) in the presence of nitrile compounds R '' CN (a:R ''=CH3; b: R ''=Ph) initially yields the corresponding eta(1)-nitrile- containing niobium(III) complexes;Nb(eta(5)- C(5)H(3)RR')(2) X(eta(1)-R '' CN) (3a, 3'a, 3 '' a, and 3 '' b) identified by electrochemical methods. These species evolve at room temperature to the more thermodynamically stable eta(2)-nitrile-containing complexes, Nb(eta(5)-C(5)H(3)RR')(2)X(eta(2)-R '' CN) (5a, 5'a, 5 '' a and 5 '' b). complexes 5a and Nb(eta(5)- C(5)H(4)SiMe(3))(2)Cl(eta(-)Ph CN) 5b were alternatively prepared and characterized from the chemical reaction of Nb(eta(5)-C(5)H(4)SiMe(3))(2)Cl 2 with a and b, respectively. Kinetic studies from electrochemical data have allowed us to establish the rate constant for the 3a-->5a isomerization process at 7.31 x 10(-5) and 5.75 x 10(-4) s(-1) at 0 degrees C and 28 degrees C, respectively (activation energy: Delta E#=55.83: kJmol(- 1)). Finally, a reverse isomerization process (eta(2)-- >eta(1) nitrile) has been observed for the paramagnetic cationic niobium (IV) complexes, [Nb(eta(5)- C(5)H(3)RR')(2)X(eta(2)-R '' CN)](+) 6 and [Nb(eta(5)- C(5)H(3)RR')(2)X(eta(1)-R '' CN)](+) 4, generated from electrochemical oxidation of the corresponding niobium (III) derivatives 5 and 3.

A. Antiñolo; F. Carrillo-Hermosilla; M. Fajardo; S. García-Yuste; M. Lanfranchi; A. Otero; M. A. Pellinghelli; S. Prashar; E. Villaseñor
Organometallics 1996, 15, 5507-5513.
Studies on the Insertion Reactions of Activated Alkynes into Nb-H Bonds in Hydride-Niobocene Complexes. X-ray Crystal Structures of Nb(h⁵-C₅H₄SiMe₃)₂(H)[h²-RO₂C(H)=C(H)CO₂R](R=Me or ^tBu)
The hydride isocyanide complexes, Nb(eta(5)- C(5)H(4)SiMe(3))(2)(H)(CNR), R=xylyl=2,6-dimethylphenyl; Cy (cyclohexyl); (t)Bu; as well as the hydride carbonyl complex Nb(eta(5)-C(5)H(4)SiMe(3))(2)(H)(CO) react with several activated alkynes to afford the corresponding alkenyl isocyanide complexes Nb(eta(5)- C(5)H(4)SiMe(3))(2)(CNR)(C(R')=CH(R '')), R=xylyl, R'=R ''=CO(2)Me 1; R=Xylyl, R'=R ''=CO(2)(t)Bu 2; R=Xylyl, R'=CO(2)Me, R ''=H 3; R=Xylyl, R'=CO(2)Me, R ''=Me 4; R=Cy, R'=R ''=CO(2)Me 5; R=Cy, R'=R ''=CO(2)(t)Bu 6; R=Cy, R'=CO(2)Me, R ''=Me 7; R=(t)Bu, R'=R ''=CO(2)Me 8; (t)Bu, R'=R ''=CO(2)(t)Bu 9 and alkenyl-carbonyl complexes, Nb(eta(5)-C(5)H(4)SiMe(3))(2)(CO)(C(R')=CH(R '')), R'=R ''=CO(2)Me 10; R'=R ''=CO(2)(t)Bu 11; R'=CO(2)Me, R ''=H 12. The reaction of hydride isocyanide complexes with activated alkynes gives cis- insertion resulting in the formation of (E)-alkenyl products. However, the hydride carbonyl derivative undergoes insertion to give, under kinetic control, a mixture of (E)- and (Z)-alkenyl isomers. Finally, the trihydride niobocene complex Nb(eta(5)- C(5)H(4)SiMe(3))(2)(H)(3), reacts with esters RO(2)CC=CCO(2)R' or MeO(2)CC=CH to give the hydride olefin derivatives, Nb(eta(5)- C(5)H(4)SiMe(3))(2)(H)[eta(2)-RO(2)C(H)=C(H)CO(2)R'], R=R'=Me 13; R=R'=(t)Bu 14; and Nb(eta(5)- C(5)H(4)SiMe(3))(2)(H)[eta(2)-MeO(2)C(H)=CH2] 15, probably as the result of a stereospecific trans- insertion. The different complexes have been characterized by spectroscopic methods. In addition, the structure of 13 and 14 were determined by single crystal X-ray diffraction.

A. Antiñolo; I. Del Hierro; M. Fajardo; S. García Yuste; A. Otero; O. Blacque; M. M. Kubicki; J. Amaudrut
Organometallics 1996, 15, 1966-1971.
Chemistry of h2-CS2 Niobocene Complexes: Synthesis and Characterization of New 1,3-dithiol-2-ylidene Complexes via Reactions with Activated Alkynes
The reaction of CS2 with Cp'Nb-2(H)(eta(2)-CH2=CH2) or Cp'Nb-2(H)(eta(2)-CH2-CHPh) (Cp' = eta(5)- C(5)H(4)SiMe(3)) affords the alkylniobocene complexes Cp'Nb-2(Et)(eta(2)-CS2-C,S) (2) and Cp'Nb- 2(CH(2)CH(2)Ph)(eta(2)-CS2-C,S) (3), respectively. The interaction of eta(2)-CS2-containing complexes Cp'2NbCl(eta(2)-CS2-C,S) with alkynes bearing electron- withdrawing groups gives rise to a new family of 1,3- dithiol-2-ylidene niobocene species, Cp'(2)NbX(=CS(R)C=C(R)S) (6, X = Cl, R = CF3; 7, X = Cl, R = COOMe; 8, X = Cl, R = COO(t)Bu; 9, X = Et, R = COOMe; 10, X = Et, R = COO(t)Bu; 11, X = CH(2)CH(2)Ph, R = COOMe; 12, X = CH(2)CH(2)Ph, R = COO(t)Bu). In a similar way, with the carboxylate complexes Cp'Nb-2(OC(O)H- O)(eta(2)-CS2-C,S) (4) and Cp'Nb-2(OC(O)CH3-O)(eta(2)- CS2-C,S) (5) as starting materials, other 1,3-dithiol-2- ylidene species have been isolated Cp'Nb-2(OC(O)Y- O)(=CS(R)C=C(R)S) (13, Y = H, R = COOMe; 14, Y = H, R = COO(t)Bu; 15, Y = CH3, R = COOMe; 16, Y = CH3, R = COO(t)Bu). The structures of all complexes have been determined by spectroscopic methods. The structure of 2 was established by single-crystal diffractometry studies. The molecular structure shows a typical bent- sandwich geometry around the niobium atom with the ethyl and carbon disulfide ligands arrayed in the plane between the two cyclopentadienyl rings.